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Peter Turchin (1957–)

Turchin brought the methods of population ecology to history. Trained to model the oscillations of animal populations, he turned in the late 1990s to the rise and fall of states and argued that history, like ecology, has regular dynamics that can be modelled mathematically and tested against data. He called the programme cliodynamics. It has two main lines: cycles of integration and disintegration within societies, which he calls secular cycles, and the growth of large states by cultural multilevel selection in competition between societies. He has also built one of the largest databases of the human past to test both.

Peter Turchin was born on 22 May 1957 in Obninsk, in the Soviet Union, the son of the computer scientist and dissident Valentin Turchin, and moved to the United States with his family after his father’s exile in 1977. He took a BA in biology at New York University in 1980 and a PhD in zoology at Duke University in 1985. His work in population ecology, on the cycles of insect and rodent populations, culminated in Complex Population Dynamics (2003). At the University of Connecticut, where he became professor of ecology and evolutionary biology and later emeritus, he moved into history with Historical Dynamics (2003), and he founded the journal Cliodynamics in 2010. He has since worked with the Complexity Science Hub in Vienna and as a research associate at Oxford, and was elected a fellow of the American Association for the Advancement of Science in 2021.

Key concepts

Secular cycles. With the Russian historian Sergey Nefedov, Turchin argued in Secular Cycles (2009) that agrarian states pass through long cycles of two to three centuries: an integrative phase of population growth, prosperity and stable government, then a disintegrative phase of crowding, inequality, elite conflict and civil war, followed by recovery. The book tested the pattern on medieval and early modern England and France, Rome and Russia. The underlying structural-demographic theory develops Jack Goldstone’s account of early modern revolutions.

Elite overproduction. Within the disintegrative phase Turchin gave most weight to elite overproduction, a growth in the number of aspirants to elite positions beyond the positions available, which turns competition among elites into factional conflict. Together with popular immiseration and the weakening of state finances, it forms the core of his model of instability. In a letter to Nature in 2010 he applied the model to the United States and western Europe and predicted that the coming decade was likely to be one of growing political instability. Ages of Discord (2016) and End Times (2023) set out the American case at length.

Asabiya and metaethnic frontiers. From Ibn Khaldun he took asabiya, a group’s capacity for collective action. War and Peace and War (2006) argued that asabiya is forged on metaethnic frontiers, where peoples of very different culture confront each other, and that the great empires arose from such frontiers and declined as their cohesion wore away in the secure interior.

The evolution of large-scale societies. Ultrasociety (2016) and a series of papers treat the growth of states as cultural evolution under multilevel selection: societies whose institutions let them cooperate at larger scale outcompeted others, above all in war. A model he published with colleagues in 2013, “War, Space, and the Evolution of Old World Complex Societies”, predicted where and when the largest societies arose between 1500 BCE and 1500 CE from the spread of military technologies such as chariots and cavalry and from geography, and matched the historical record better than models without warfare.

Seshat. To test these theories he co-founded, with Harvey Whitehouse and Pieter François, the Seshat Global History Databank, which codes the institutions, economies, religions and warfare of polities across ten thousand years so that hypotheses about the past can be checked against systematic data.

Where Turchin stops

A 2019 Nature paper by the Seshat team, Turchin among its authors, arguing that complex societies preceded belief in moralising gods, was retracted in 2021 after Bret Beheim and colleagues showed that missing observations had been coded as absences. A re-analysis followed in 2022.

Key works

Complex Population Dynamics: A Theoretical/Empirical Synthesis (2003)
Historical Dynamics: Why States Rise and Fall (2003)
War and Peace and War: The Life Cycles of Imperial Nations (2006)
Secular Cycles, with S. A. Nefedov (2009)
“Political Instability May Be a Contributor in the Coming Decade”, Nature 463 (2010)
“War, Space, and the Evolution of Old World Complex Societies”, with T. E. Currie, E. A. L. Turner and S. Gavrilets, PNAS 110 (2013)
Ultrasociety: How 10,000 Years of War Made Humans the Greatest Cooperators on Earth (2016)
Ages of Discord (2016)
End Times: Elites, Counter-Elites, and the Path of Political Disintegration (2023)